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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 57: Organic Electronics and Photovoltaics IV - Excitonic Properties and Light-Emitting Devices

CPP 57.1: Vortrag

Donnerstag, 4. April 2019, 15:00–15:15, H18

Optical Probing of the Various Operation Regimes in Organic Light-Emitting Diodes Using Molecular Probes — •Thomas Ferschke¹, Alexander Hofmann², Wolfgang Brütting², and Jens Pflaum^1,3 — ¹Experimental Physics VI, Julius Maximilian University, 97074 Würzburg — ²Institute of Physics, University of Augsburg, 86135 Augsburg — ³ZAE Bayern, 97074 Würzburg

Photoluminescence (PL) studies on single guest molecules have been shown to enable determination of charge carrier distribution in organic opto-electronic devices on nanometer length scales.[1] In this work, this principle is adapted to the various operation regimes of Alq₃/α-NPD OLEDs. Tetraphenyldibenzoperiflanthene (DBP) dopants are incorporated at distinct vertical positions within the active layers of the OLED stack. Measuring the DBP optical properties under different operation conditions of the device, the significant reduction in PL upon charge carrier injection (forward bias regime) can be attributed to non-radiative decay channels promoted by the exciton-electron interaction. Studying this effect as function of current density and dopant position reveals information on the local charge carrier distribution. Under reverse bias, a strong PL quenching of DBP probes in close proximity to the Alq₃/α-NPD interface is observed as well. This can be related to the strong electric fields caused by Alq₃ charges localized at the interface.[2] We substantiate this hypothesis by complementary data obtained by impedance spectroscopy on the identical OLED devices.

[1] Nothaft et al., ChemPhysChem, 2011, 12, 2590–2595

[2] Noguchi et al., J. Appl. Phys., 2012, 111(11):114508